Patent Document 1 discloses that a controller of a multiphase AC motor uses an average value of output currents of plural inverters connected, in parallel, to the multiphase AC motor, as a feedback signal sent to a main current control system provided on a rotating coordinate system of the AC motor, and uses a differential value of output currents of the respective inverters as a feedback signal sent to a current control system for controlling unbalanced currents which is provided on the rotating coordinate system of the AC motor.